As birds die of bird flu, authorities have also noticed that the deadly strain of the virus, called H5N1, is infecting increasing numbers of mammals.
Mink-to-mink transmission has drawn attention to potential risks to humans, but experts say there’s no need to panic.
H5N1 bird flu spreading to mammals, health officials urge caution
This week, the World Health Organization (WHO) urged authorities to remain vigilant – but without panicking – about the potential risk of the virus to humans.
“The recent spread of the virus to mammals should be watched closely,” said Wednesday Tedros Adhanom Ghebreyesusdirector general of the WHO, to journalists, according to theFrance Media Agency (AFP). But “for the moment, the WHO considers that the risk for humans is low”.
Avian influenza is not adapted to infect humans, making human cases rare and person-to-person transmission even more difficult. But experts say the more H5N1 spreads among animals, the more likely it is to evolve into a variant capable of jumping to humans, according to AFP.
Despite the current low risk to public health, officials must be prepared “to deal with outbreaks in humans, and also be ready to control them as soon as possible”, says to Erin Prater of Fortune Sylvie BriandDirector of Global Infectious Hazard Preparedness and Emergency Preparedness at WHO.
H5N1 was first detected in domestic waterfowl in 1996 and spread to migratory birds around 2005. These long-distance flying birds then carried the virus around the world, writes Kai Kupferschmidt of Science . During this period, the virus infected relatively few humans, but these cases proved fatal. According to the WHO, there were 868 global cases of H5N1 in humans between January 2003 and November 2022, of which 457 were fatal.
Currently, a massive outbreak of bird flu is raging around the world. The United States is experiencing the worst outbreak of bird flu in its history, with the virus directly or indirectly killing 58 million birds last year, according to Fortune. Europe is also experiencing its worst outbreak, according to AFP.
“With high levels of transmission, we are seeing unprecedented numbers of dead birds and disease outbreaks,” says Michelle Willan avian flu researcher at the University of Sydney in Australia, to Liam Mannix of the Sydney Morning Herald.
The H5N1 virus does not tend to infect mammals because they have fewer receptors in their upper respiratory tract to which the virus attaches.
But during this year’s outbreak, foxes, raccoons, bears and other mammals caught the virus. In the United States, infections in mammals have been detected in nine different states, according to USA Today’s Adrianna Rodriguez. In Peru, at least 585 sea lions have been found dead, possibly due to bird flu. Other infected animals include dolphins and possums, according to Fortune.
Most of these cases are likely due to a mammal eating an infected bird, Jürgen Richt, who studies avian flu at Kansas State University, told USA Today. But in an article published in January in the journal Eurosurveillance, researchers provide evidence that the virus may have spread between mink on a farm in Spain last October. Genetic sequencing has revealed a genetic modification known to make certain flu viruses better able to reproduce in mammals, writes Nature News’ Saima May Sidik.
The mink outbreak has “confirmed a fear I had” that bird flu could spread effectively among mammals, Thijs Kuiken, a veterinary pathologist at Erasmus University Medical Center in the Netherlands, told The Times. Down.
“We have never seen mammal-to-mammal transmission, ever. It never happened,” Wille told the Sydney Morning Herald. “Now it’s not just a guess anymore. Now we have actually seen it happen”.
Experts say this development is not cause for alarm. “It’s not, in my view, a particularly worrisome situation for human health,” Jim Lowe, a veterinarian at the University of Illinois at Urbana-Champaign, told The Times. “Obviously it’s not very good for the mink.”
Mink caged and huddled together may have transmitted H5N1 due to their conditions rather than a fundamental change in the virus, Frank Wong, an avian flu expert at the Scientific Research Organization, tells the Sydney Morning Herald. and Industry of the Commonwealth of Australia. “It is still a virus adapted to birds”.
But evidence of mammal-to-mammal spread is also a warning sign, other people say. “This outbreak signals the very real potential for mammal-to-mammal transmission to emerge,” Wille told CBC News’ Lauren Pelley in an email.
“We need to be vigilant to make sure the spread in animals is contained,” Briand told AFP. “The more the virus circulates in animals, the higher the risk for humans as well.”
Source: Smithsonian Magazine